Пример #1
0
        private Stmt ForStatement()
        {
            Consume(TokenType.LEFT_PAREN, "Expect '(' after 'for'.");

            // If the token following the ( is a semicolon then the initializer
            // has been omitted. Otherwise, we check for a var keyword to see
            // if it’s a variable declaration. If neither of those matched, it
            // must be an expression. We parse that and wrap it in an expression
            // statement so that the initializer is always of type Stmt
            Stmt initializer = Match(TokenType.SEMICOLON)
                ? null
                : Match(TokenType.VAR)
                    ? VarDeclaration()
                    : ExpressionStatement();

            // If next token is a semicolon then the condition has been omitted.
            Expr condition = Check(TokenType.SEMICOLON) ? null : Expression();

            Consume(TokenType.SEMICOLON, "Expect ';' after loop condition.");

            // If next token is closing right paren, increment ommitted.
            Expr increment = Check(TokenType.RIGHT_PAREN) ? null : Expression();

            Consume(TokenType.RIGHT_PAREN, "Expect ')' after for clauses.");

            var body = Statement();

            // Add the increment expression evaluation to end of body if not null
            if (increment != null)
            {
                body = new Block(new List <Stmt> {
                    body, new Expression(increment)
                });
            }

            // Wrap the body into a while based on condition. If null then set
            // condition to true (infinite loop)
            if (condition is null)
            {
                condition = new Literal(true);
            }
            body = new While(condition, body);

            // If initializer was set, wrap body in block with initializer to run
            // first before the loop body is executed
            if (initializer != null)
            {
                body = new Block(new List <Stmt> {
                    initializer, body
                });
            }

            return(body);
        }
Пример #2
0
 public string VisitWhileStmt(While stmt)
 {
     throw new System.NotImplementedException();
 }
Пример #3
0
 public object VisitWhileStmt(While stmt)
 {
     Resolve(stmt.Condition);
     Resolve(stmt.Body);
     return(null);
 }